The invention relates to a releasable ski binding having a boot or sole holder which swivels around a ski-side vertical shaft when it is released. The boot or sole holder is pushed into its normal position which fixes the boot or the sole essentially firmly on the ski by means of a piston which is acted upon by spring force and which can be slid in the longitudinal direction of the ski inside a guide which is non-rotatable with respect to the vertical shaft. Projections and recesses on the boot-holder-side or sole-holder-side end of the piston are held in a centering engagement with recesses or projections of the boot holder or sole holder on both sides of a vertical plane containing the vertical shaft and extending in the longitudinal direction of the ski by mean of the spring force pushing against the boot holder or sole holder.
In ski bindings of this type, as they are known, for example, from the German Patent Document DE-AS 22 14 091 as well as from the French Patent Document FR-OS 25 11 602, the boot holder or sole holder as well as the piston in the normal position form a virtually rigid unit held together by the spring force which can carry out movements only within the scope of the play of the piston within the guide or of the play of the boot holder or sole holder on the vertical shaft. It is only when the forces acting upon the boot holder or sole holder are large enough for canceling the virtually rigid connection between the piston and the sole holder or boot holder caused by the spring force that the boot holder or sole holder can carry out a release swivel which is sufficient for the release of the boot and during which in each case one side of the boot holder or sole holder on one side of the above-mentioned vertical plane continues to be pushed by the piston into the direction of the normal position, while the respective other side of the boot holder or sole holder lifts off the piston and is no longer acted upon by forces.
In the case of the previously known bindings of the initially mentioned type, a comparatively high amount of friction, as a rule, must be expected during the release swivel between the binding elements moving relative to one another. The reason is that, in order to hold the boot holder or sole holder in the normal position with as little play as possible, the guide is dimensioned to be as narrow as possible in order to avoid a play of the piston in the transverse direction of the ski. As a result, considerable frictional resistances may occur between the piston and the guide because of even a slight accumulation of dirt and may counteract a sliding of the piston during the release swivel. It is an additional fact that the one side of the boot holder or sole holder which during the release swivel in each case remains in a force-locking contact with the piston, in the course of the release swivel, travels through a curved path and thus also carries out a movement in the transverse direction of the ski. However, the piston, in the case of the previous bindings cannot follow this component of movement in the transverse direction of the ski because of its bearing in the guide that is largely free of play in the transverse direction of the ski. Consequently, during the release swivel considerable relative movements having friction occur between one side of the boot holder or sole holder and the piston; i.e., the release swivel is counteracted by an additional considerable frictional resistance which is very dependent on dirt accumulations at the areas of the boot holder or sole holder and the piston which slide on one another.
Apart from the fact that frictional resistances which depend on the accumulation of dirt are undesirable because they result in a release action of the binding that is hard to reproduce, the friction causes a basically undesirable hysteresis within the elasticity range of the binding. This means that the forces which restore the boot holder or sole holder with a slight deflection within the elasticity range of the binding to the normal position under certain circumstances may clearly be lower than those forces on the boot side or sole side which previously have caused the deflection.
It is therefore an object of the invention to keep the internal friction of the binding as low as possible with minimal constructional expenditures.
In the case of a binding of the initially mentioned type this object is achieved in that the guide guides the piston without play in the transverse direction of the ski only in the are of its end which is away from the boot holder or sole holder, and the end of the piston which is on the boot holder or sole holder side, during the release swivel of the boot holder or sole holder, virtually without any force is able to follow at least a first section of a curved path through which the side of the boot holder or sole holder travels in each case which remains in an engagement with the piston in the respective release direction by way of the projection and the recess or the projections and the recesses.
The invention is based on the general idea of arranging the boot-holder-side or sole-holder-side end of the piston to be movable in the transverse direction of the ski so that the projection and the recess or the projections and the recesses which remain in an engagement during a release swivel of the boot holder or sole holder, only interact with one another in the manner of joint elements and correspondingly larger sliding movements are avoided between these elements relative to one another. As a result, the friction between the piston and the boot holder or sole holder can be reduced quite considerably.
As a result of this construction, essentially only the end of the piston that is away from the boot holder or sole holder is guided without any play which, by a corresponding construction of the binding, without any major expenditures, can be protected against becoming dirty so that the friction between the piston and the guide also becomes negligible.
According to a preferred embodiment of the invention, it is provided to construct the binding in such a manner that the projections and recesses in the normal position on the side of the boot are situated in a vertical plane containing the vertical shaft and extending in the transverse direction of the ski, in such a manner that, during the release swivel, projections and recesses remaining in an engagement with one another in each case on one side of the boot holder or sole holder, take up a position on the other side of this vertical plane during a maximal swivelling of the boot holder or sole holder and the distance from this vertical plane is approximately the same as in the normal position.
In this construction, the transverse movement of the boot-holder-side or sole-holder-side end of the piston which occurs during the release swivel of the boot holder or sole holder remains particularly slight. As a result, the friction, which may occur between the piston and the guide because of the transverse movement of one piston end, is kept particularly low.
It is also expedient for the guide to be open only on its boot-holder-side or sole-holder-side end--for the piston parts projecting out of the guide--, and the space between the guide and the boot holder or sole holder is closed off by a bellows-type covering.
Thus, it can be avoided in a constructively particularly simple manner that the elements which are essential for the release resistance of the binding become dirty.
In addition, it is preferably provided that the projections are constructed as narrow strips, wedges or the like which virtually only have line contact with the assigned recesses. This arrangement in connection with the transverse mobility of the boot-holder-side or sole-holder-side end of the piston results in an almost complete absence of friction between the piston and the boot holder.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.